Many of us spend a lot of time trying to figure out how to reduce our consumption of calories — but what if you wanted to maximize your calories per bite? What food would you eat to make sure you were taking in the greatest amount of energy? This may seem like an academic question now — but after the zombie apocalypse, you'll need this information.

"That's actually not such a crazy question," says Brian B. Parr, Associate Professor of Exercise and Sports Science at the University of South Carolina Aiken. It's the sort of thing that "adventure racers" and mountaineers who hike across the country worry about — and that's the reason why they'll carry highly portable foods that are high in calories, like nuts, salami and jerky with them. Also sometimes people will cook some rice and put an entire stick of butter in, to create a portable calorie-dense food source on treks.

And what food has the most calories? In a nutshell, fat. "Gram for gram, ounce for ounce, fat has the most calories," says Lisa Young, an adjunct professor at New York University and author of The Portion Teller Plan. So oil, cream, butter and lard are all excellent candidates.

Something like a cheeseburger will be high in calories — but it's not pure calories, because both the cheese and the meat also have protein and carbohydrates, says Young.

Similarly, I was wondering about the deep-fried Oreos I see being advertised as a snack in some of the Chinese diners here in San Francisco. Wouldn't those be pretty high in calories? Yes, says Parr, because the Oreos are already fatty and then deep-frying them just adds another layer. But they wouldn't be pure calories, cautions Young — there are still some carbohydrates mixed in. If you want just pure calories, you want butter or oil — but you couldn't live on just butter or oil, adds Young. Image via PatrickD/Flickr.

Plus of course, there's the problem that eating nothing but pure lard would be disgusting and taste horrible, notes Lisa Te Morenga, a research fellow in the Department of Human Nutrition at the University of Otago in New Zealand. You might be better off eating a lot of something like chocolate or salted nuts, which is less "energy-dense" but tastier.

And if you want to take in a lot of calories in a short time, you could do worse than eating a milkshake, notes Parr. Recently, one fast food chain was selling a milkshake that was 2,000 calories, allowing you to consume your entire recommended daily caloric intake in a few quick gulps. When it comes to giving you "a ridiculous amount of calories really quickly," a milkshake is great, says Parr.

What if you could only eat a few ounces per day?

Suppose someone told you that you could only eat a few ounces of food per day. What would be the best food to make sure you got enough energy to keep going?

If this was for a short-term, endurance-type event, pure fat would be ideal, says Morenga. But you can't live on just fat long term, because you need essential amino acids, vitamins and minerals. So something like an avocado would be perfect, says Young, because it's high in fat as well as protein and other stuff.

And you'll also want to try and get some carbohydrates, adds Parr. An athlete who's in training, say for the Tour de France, will eat up to 10,000 calories per day, says Parr. But they'll need a lot of carbohydrates in addition to a lot of energy to sustain their training.

This is also a question that survivalists think about a lot, according to Parr. These people think about being stuck in a shelter for years, so they "want a small amount of food with the most calories" — and they tend to reach for things like candy bars, that also have protein and carbs. So after the zombie apocalypse, you may want to have a wall of Snickers bars ready.

After all, says Parr, the zombies are thinking about the same concern: they don't eat fruits or vegetables, they eat people, who are a high-calorie food source. In particular, zombies tend to go for our brains — which are just soaked in fat, and thus pack a lot of calories in a relatively small nugget. So when you're surviving the zombie apocalypse, it might be helpful to think a little bit like a zombie. Image via Ginnerobot/Flickr.